Private constructor in java example

Constructor in java:

• Constructor is used to initialize class variables.
• Constructor will be executed once per object and whenever object is created constructor will be called.
  

Private Constructor in java:

• We can make constructor private, public , protected and default.
• If we define a constructor as private means we are restricting a class to create object  outside of the class.
• A class having private constructor does not allow user to create object outside.
• In singleton Design pattern we will use private constructor to restrict object creation

1. package inheritanceInterviewPrograms;
2.  
3. public class A {
4.   
5.   private A(){
6.        
7.        
8.    }
9.  
10. public static void main(String args[]){ 
11.    
12.       A s= new A();
13.   }
14.  
15. }

1. package inheritanceInterviewPrograms;
2. //  www.instanceofjava.com
3.  
4. public class B {
5.     
6. public static void main(String [] args){
7.      
8.     A obj= new A();// Compile time error
9.    
10.  
11. }
12. }

• To understand real use of private constructor please check Singleton Design Pattern in java